This amplifier is typically built following the
electronic amp-designing and building practises of that time,
the wiring and topology is not to modern standards, some materials are not to
todays standard.

Modifications:

Power supply:

It is easy to upgrade this amp to
modern standards.
Change the power supply to star topology.
Change or add sufficient uF in the main power supply, initial C1 2200 uF is not
up to modern standards.
Check wire gauge of the power supply.
Check all caps in the power supplies.

Power amp:

The resistors of 10 Ohms R20, R20a in the power amp are always burnt, replace
them for 1 Watts type.
The capacitors C1(a) and C5(a) should be replaced by audio caps.
If you are in Europe set the voltage selector to 240 Volts.
Check DC offset and idling current of the power amp.
Check wire gauge of the power amp, and speaker wires: they are rather thin.
Check TR1 and TR2, they break down easely.
Check all caps in the power amp.

Pre amp:

Do usual parts checks for all pre
amps.
The transistors can get noisy and the caps may have broken down after many years
of service.